The present invention relates to a method for operating a purification device for flowing gases, particularly for exhaust gases of internal combustion engines, wherein the purification device comprises a filter body through which fluids can flow and which comprises a catalyst which is exposed to the gas stream, wherein a reducing agent is added to the gas before the gas enters the catalyst, to a purification device for purifying gases, comprising a filter body which comprises a catalyst and through which fluids can flow, wherein the filter body is disposed in the gas flow, and wherein the filter body purifies the gases with the help of a reducing agent, as well as to the use of such a purification device, wherein such a purification device is useful in automobiles to decrease pollutants.
Published German Patent 44 20 932 discloses a catalyst for a purification device for exhaust gases of a diesel engine which is made of a spinel. The catalyst has a high resistance to substances present in the exhaust gas. However, the reduction of the nitrogen oxides is limited to 40% at most.
It is an object of the present invention to develop a method which lowers the emission of pollution. Furthermore, it is an object of the present invention to provide a purification device which lowers the emission of pollution.
Pursuant to the present invention, these and other objectives are accomplished by a method comprising the steps of
adding more reducing agent to the gas after a certain treatment point wherein the gas to be purified has passed through the catalyst of the filter body, and PA1 maintaining contact between the gas and the catalyst of the filter body.
These and other objectives are also accomplished by a purification device wherein the purification device comprises a mechanism for feeding reducing agent to the gas as it flows through the filter body.
By adding reducing agent at a point after which the catalyst no longer has any catalytic effect with respect at least one of the pollutants, the reduction of pollutants, particularly of nitrogen oxides, can be increased to more than 40%.